If gender is a societal construct with associated roles, (allegedly now obsolete) then there would not be the feeling or need to change one's gender.
I don't think you understand dysphoria, or trans people's desire to transition, in general.
I'm going to copy and paste something I said here once.
"To address some of these points, I'd like to share my perspective as a binary trans person. I can't say I understand nonbinary identities, but at least for binary identities, we usually
do identify with the
SEX characteristics of our target sex,
rather than just the gender identity.
When I was a kid, barely acquainted with gender roles, I still knew I wanted a penis. I thought I was a boy and didn't underneath why I didn't have one. I didn't understand why I got in trouble when I went into the boy's bathroom. Etc.
Going through puberty, I had massive dysphoria about my female parts themselves, and massive dissatisfaction about not having a penis, not having facial hair, etc. In all of my dreams, my brain depicted me as a male. I even had phantom limb sensations where I would feel I had a penis even though I didn't, similarly to how a amputated person still has sensations of their missing limb.
I didn't just have dissatisfaction about not fitting into a social role of "man", I LITERALLY felt a disconnect between my brain and my physical
sex ... not gender.
And I do not get gender roles, gender, and sex confused these days.
Now that I am fully transitioned and have the things I wish I was born with (besides my chromosomes, but I can't see those, and no one else can, either, so it doesn't really bother me), I feel perfectly comfortable with my partner dressing me up or putting nail polish on me. I don't quail when I enjoy stereotypically feminine hobbies. On Halloween last year, I even put on a woman's bunny costume along with all of my cisgender male friends when we went to a Halloween party, because it's just a fun time to twist gender roles, and I am a man. Whether or not I wear woman's clothing doesn't dictate that. If I felt like my clothing choices had anything to do with my gender, than I'd be confused.
To me, nothing about the hobbies I enjoy or clothes I'm willing to wear determine my identity.
I don't identify with male stereotypes, I identify with the male body. Being a tomboy isn't what I needed, being as close to a biological MALE is what I needed.
I didn't need to wear a masculine outfit, or drive a pickup truck... I needed a penis and balls.
That's a lot of private information, I know, but I hope this made sense about why trans people don't necessarily fall for gender roles as much as many of us identify with a biological sex.
For nonbinary people, though, it might be different."
Gender roles are not what makes trans people. Trans men are inherently different than tomboys.